Not Applicable.
1. Technical Field of the Invention
The present invention relates generally to gypsum board and methods for making gypsum board. More specifically, the present invention relates to gypsum board possessing antifungal properties and methods of making same.
2. Description of Related Art
Gypsum board, which is sold as wall board and drywall, is a common building material used in various applications including interior walls, partitions and ceiling construction. Commercial gypsum board products are popular for a variety of reasons. They are durable, economical and fire-retardant. In addition, these boards provide excellent compressive-strength properties and a relatively low density. Finally, they are easily decorated and are therefore attractive as surfacing materials, especially for interior construction.
One fundamental limitation of traditional gypsum board products is their susceptibility to moisture absorption in damp environments. To minimize this problem, gypsum board is normally used in interior construction where exposure to moisture is limited. Unfortunately, products used in interior construction sometimes encounter water due to seepage, leaky roofs or pipes, flooding, condensation, and the like, arising out of construction defects or other events unrelated to the manufacture of the gypsum board. Thus, a number of mechanisms result in the exposure of gypsum board products to moisture. Once exposed to moisture, traditional gypsum board products are susceptible to fungal growth.
There is an ongoing need for gypsum board products that offer reduced susceptibility to fungal growth without compromising their beneficial properties. In addition, there is an ongoing need for commercially-viable manufacturing methods for such products. The present invention solves these problems by using an antifungal agent that effectively inhibits fungal growth, is compatible with gypsum board materials, and can be incorporated into a cost-effective and commercially-viable manufacturing process.
The preferred embodiments of the present invention include a novel gypsum board comprising an effective amount of an antifungal agent such that fungal growth on or in the board is inhibited. According to a preferred embodiment of the present invention, the antifungal agent is cetyl pyridinium chloride (CPC), a quaternary ammonium compound. Preferably, the gypsum board comprises from about 0.01 to about 1.5 weight percent CPC based on the dry weight of the gypsum in the board. More preferably, the gypsum board comprises between about 0.5 and about 1.0 weight percent CPC based on the dry weight of the gypsum in the board. According to some preferred embodiments, the CPC is encapsulated in an encapsulator so that it is released over time and/or upon exposure to moisture.
The preferred embodiments of the present invention also include methods of preparing the novel gypsum board described above. According to some preferred embodiments, CPC is incorporated onto or into the gypsum core by premixing CPC with the water, premixing the CPC with the gypsum powder, admixing the CPC with both the water and gypsum powder prior to or in the slurry mixer, and/or adding CPC to a mixed gypsum slurry via a secondary or in-line mixer. According to other preferred embodiments, a CPC solution is sprayed onto the front and/or back paper facings. According to other preferred embodiments, CPC is incorporated into the front and/or back paper facings as they are manufactured.